While Caterpillar believes mechanical drive is the best solution for the vast majority of situations, the company listened to its customers and explored the situations and conditions where electric drive would be the preferred option. Cat is the only manufacturer of 200-ton and above mining trucks with both drives.

Cat will produce mining trucks for every application—uphill, downhill, flat or extreme conditions—and now with electric as well as mechanical drive.

—Chris Curfman, president of Cat Global Mining & vice president of Caterpillar Inc.

At MINExpo 2008, Caterpillar will introduce four new trucks. The 793 series in the 240- to 250-ton class will be available in both mechanical (793F) and electric (793F AC) versions. The 345-ton 795F AC, a new size for Caterpillar, will be available in electric drive only, while the flagship 797B is replaced by the new 797F mechanical drive, maintaining its 380- to 400-ton target payload.

The 797F and 795F AC, along with the recently introduced 777F, will be displayed on the exhibit floor. Completing Caterpillar’s new mining truck line will be new versions of the 785 and 789 mechanical drive trucks, upgraded to meet customer requirements for safety, serviceability, operator comfort and emission standards.

In the late 1960s Caterpillar was one of the first manufacturers to commercialize electric-drive trucks but elected to focus its design and development efforts on mechanical drive. With advances in AC drive technology, coupled with proven components and technologies from existing Caterpillar products, the company concluded it was the appropriate time to make electric drive available to its customers as a complement to its mechanical drive.

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The next generation of trucks will be phased into production over the next two years, with the Cat AC drive models expected to go into production in late 2010.

These are trucks for mining operations which means they are used only in a local area. Consequently, the electric versions do not need a range extender or diesel generator. Instead, they can use large swappable batteries that they can swap in a few minutes at a local swap and recharging station. A 300 tons miming truck should easily be able to fit in two 2 ton battery modules with a total of 400 kWh of power. The world record until now for electric trucks is this 30 tons electric container terminal truck from http://www.balqon.com/index.php

I am convinced the economics of heavy duty local service trucks is very promising as it is now with $100 oil and these new very durable and high power lithium batteries.

The economics don't seem to work out Henrik, at least not yet. While I imagine there is some optimization wrt battery pack size and operating time, if we simply replace all the diesel carried with A123 cells, the hauling capacity would drop by about a third. Even if the cells are used down to ~50% of capacity, at roughly 10,000 equivalent full cycles, they will still cost ~$.15/kWh. Tack on electricity at ~$.05c/kWh and we're at ~$.20c/kWh. With diesel fuel at $4/gallon, that's ~$.10c/kWh, or ~$.25c/kWh delivered to the wheels given the relatively high efficiency of larger diesels. The problem is that since battery weight decreases capacity by a third give or take, the vehicle will need to operate 1.5 times more than it would have as a diesel, so the cost of an electric (batteries/electricity) would then be correspondingly higher at around $.30/kWh. That being said, there's probably some combination of pack size/charging window that's optimal, so it's probably less than this. In any event, from what I've read, in the volumes needed for this sort of work, synthetic fuels are economically viable at these prices, so I'm not sure if we'll ever see all electric HDVs like mining trucks outside of specialized roles.

The quote mentions some vehicles are used for downhill operation. If a truck is filled-up at the top of a hill, could it use the weight of its load to help recharge supercaps or batteries, and then go up hill on electricity when it is lighter as it has no load?

These are electric drive not bev as in a generator provides all the power all the time and not any battery. These behemoths use gargantuan motors and a rather massive generator is used to provide the power.

Knowing the weight of fully loaded trucks (250 tons - it's about half the weight of smaller passenger train), the most natural choice seems to be something like Diesel-Electric locomotive drivetrain.

It drops mechanical transmission for more reliable AC drive with inverter.

Plug-in or battery swapping don't seem very likely at this stage of batteries development (and availability).

Electric drive trucks may have advantage at sites where load is mostly driven downhil - by applying e-motor braking it greatly reduces brake wear and therefore downtime (for mainteinance)) of the very expensive trucks.

These trucks often operate at mining sites in wilderness where diesel generators are used for electricity - for them any plug-in is not an economical option, would mean waste of diesel fuel.

Considering that many of these trucks operate 24/7, and diesel heat is freely available, Zebra batteries could be suitable.

Mohsen, I stated that down to 50% dod (approximately 4% capacity loss every thousand cycles) they would be equivalent to 10,000 complete (100% dod) cycles. No that they would only do 10,000 cycles at 50% dod.

In any event, even that depends on how they're used. Like most other batteries the discharge rates greatly influence pack lifespan, and I'm not sure if we could count on the low (1C IIRC) rates needed to see a longer lifespan in these applications.

Almost forgot. As for A123's prices dropping, I'm not sure if that would be passed onto the consumer, at least until there is sufficient production for the market. As of right now people will pay more for a better battery.

There are NO batteries and NO regeneration here. These are electric transmissions, like in the Diesel-Electric locomotive and many, many applications where it is impractical to design and manufacture a huge mechanical transmission.
Just as stated by:
Reality Czech 'The article says "electric drive", not "electric power"'.
and
wintermane "These are electric drive not bev ...."
and
Mikey "I don’t think that these designs use any form of regen. .."
And it’s NOT about time the heavy hauling mining, and material industries caught on - electric drive is just another type of transmission.

@ToppaTom:
There IS regeneration here.
Only the regenerated el energy (when braking, and going downhill) is wasted as heat on large resistors, not saved in batteries.
Regen braking reduces brake wear (of mechanical brakes).
The same is often done on el locomotives for the same reason.
Next step would be to add large batteries and save that energy.

These trucks have a huge variation in power requirement, so in theory some from of energy storage (super caps?) could significantly reduce the size of the required diesel generator and allow the generator to run at an optimum speed.

A smaller diesel could be a lot cheaper.

This is really a power requirement. What's needed? 500KW for 5 minutes?

General Electric has successfully tested ZEBRA batteries for regeneration is similar mine vehicles. Any lithium batteries were rejected right off because they need to be kept cool and are not robust. Ultra-capacitors can put out a lot of horsepower but only for a few seconds. The use of D-Cell sized ultra-capacitors would recover the truth about the American name for electric torches FLASHLIGHTS. Ultra capacitor cells do work well in the CSIRO lead acid ultra battery. Perhaps the EFFPOWER bipolar battery could be modified to incorporate them as well. The battery cells prevent the ultra capacitors from overcharging. ..HG..